So we understood the mechanics of this fight but every time we were all out of range during phase 2 he would reset.
After a couple of hours we were setting up for another attempt and his room filled with Risen. When we went back to repair, we realized the whole dungeon had respawned.
Even with people still alive he would reset during phase 2. I don’t know what’s going on but Anet needs to give more incentive to do these dungeons.